He may be a nigjt owl..lol. My son was the same way and he is 4 now and is still a night owl and sleeps in. Good luck
Your baby is having less and less room in the womb so they do slow down on their movement. If you are concerned though then you should call your ob/gyn or midwife.
But it's like no movement during the day and when about 9:30pm hits, he moves 2-3 hours constantly. Then stops. If he sleeps this much outside of womb, id be terrified!
It sounds like your baby is starting to practicing for life out of the womb. Taking naps and waking up to stretch, eat, potty and back to sleep again.